Catheters are being used increasingly as a means for delivering diagnostic or therapeutic agents to internal target sites that can be accessed through the circulatory system. For example, in angiography, catheters are designed to deliver a radio-opaque agent to a target site within a blood vessel, to allow radiographic viewing of the vessel and of the blood flow characteristics near the release site. For the treatment of localized disease, such as solid tumors, catheters allow a therapeutic agent to be delivered to the target site at a relatively high concentration with minimum overall side effects. Methods for producing localized vaso-occlusion in target tissue regions, by catheter injection of a vaso-occlusive agent have also been described (U.S. Pat. No. 4,708,718 for "Hyperthermic Treatment of Tumors").
U.S. Pat. No. 4,739,768 describes a catheter having a guide wire. The catheter may be guided from an external body access site such as through the femoral artery, to an internal tissue site. The catheter progresses through a tortuous path of at least about 5 cm through vessels of less than about 3 mm inner diameter. The catheter has a relatively stiff segment dimensioned to track the wire from the access site to a region adjacent the internal tissue, and a relatively flexible remote segment dimensioned to track the wire along the tortuous path within the soft tissue. In a method for injecting a fluid into a tortuous path site, the guide wire and catheter are moved as a unit to a position adjacent the target tissue. The wire is then advanced ahead of the catheter along the tortuous path within the tissue. The catheter then tracks the wire to move along the wire's path. Once the tip of the catheter reaches the chosen site, the guide wire is removed and the selected treatment or diagnostic fluid is delivered to the target site.
The present invention is a catheter assembly useful for the delivery of diagnostic or therapeutic agents to remote portions of the vascular system, particularly to diagnose or to treat intravascular occlusions that result from embolus or thrombus formation. The invention also includes a process for delivering fluids to those vascular regions by controlling the exit rate at the remote tip.